Dec. 13, 1915 
Activity of Soil Protozoa 
483 
than three times, a new sample being taken every two minutes; during 
the examinations the respective samples were kept at the different tem¬ 
peratures. Sterile tap water of the same temperature as that at which 
the respective soils were incubated was used in making the examina¬ 
tions. Each series of samples were kept screened from the light during 
the period of incubation. After examination the samples were again 
weighed to determine the quantity of soil used in examination. Daily 
examinations of each sample of each soil were made for a period of 
eight days. (See Table III.) 
Table III .—Presence of active protozoa in different soils , with varying amounts of 
moisture at different temperatures {constant and variable) for a period of eight days 
Lab¬ 
ora¬ 
tory 
No. 
Kind of soil. 
Mois¬ 
ture 
added 
to 50 
gin. of 
soil. 
Mois¬ 
ture 
content 
Tem¬ 
pera¬ 
ture of 
incuba- 
tion.a 
Presence of protozoa after inoculation 
(days). 
Relative moisture. 
on the 
oven- 
dry 
basis. 
X 
2 
3 
4 
5 
6 
7 
8 
X2II 
X 2 I 2 
1213 
1214 
1 3 11 
1312 
1313 
1314 
X 4 II 
1412 
1413 
1414 
Green house 
soil. 
.do. 
Gm. 
0 
4.96 
9. 92 
I 4 * 95 
0 
4-47 
8*93 
13*41 
0 
3*48 
6- 95 
10.41 
Air-dry. 
Per ct. 
0.69 
9.64 
17.12 
23*54 
.28 
8.46 
15*39 
21.37 
• 14 
< 5 . 63 
12. 32 
17 * 34 
# C. 
15 to 17 
A optimum.... 
1 optimum. 
.. .do... 
.do. 
Orchard soil... 
.do. 
zA optimums,.. 
Air-dry. 
.. .do... 
A optimum ... 
1 optimum. 
.. .do... 
.do. 
zA optimums... 
Air-dry. 
Field soil. 
.. .do... 
.do. 
.do. 
.do. 
% optimum. 
.. .do... 
1 optimum. 
.. .do... 
zA optimums... 
.. .do... 
&s.c.t. 
a The writer did not think it advisable to include the remainder of Table III representing samples incu¬ 
bated at s° to 7®, 22® to 24®, 32® to £3®, and at the outdoor temperature, as in no case were any living 
protozoa found during the period of eight days. 
& S. C.t=few small ciliates. 
Upon examining Table III it is seen that in but one sample of soil 
(the field soil which had an optimum and a half of moisture) were any 
active protozoa observed. It was noted that there was a little de¬ 
pression in the sample of soil and a little free available water was 
present, thus no doubt accounting for the presence of this organism on 
the third day of incubation, as on no other day and in no other soil were 
any motile protozoa seen. 
In order to be certain that these soils contained cysts of protozoa and 
to collect some data as to the amount of moisture necessary for excyst- 
men t and also to note the time of excystment of protozoa when condi¬ 
tions are favorable, to each series of the three different soil samples con¬ 
taining moisture to the amount of half optimum and optimum and a half 
sterile tap water was added to make the amount two optimums and two 
and one-half optimums, respectively. These samples were then incu¬ 
bated at the same temperatures as before, and daily examinations for a 
period of four days were made. (See Table IV.) 
